As the semiconductor industry has strived for higher device density, higher performance, and lower costs, problems involving both fabrication and design have been encountered. One solution to these problems has been the development of a fin-like field effect transistor (FinFET). A typical FinFET includes a thin vertical “fin” formed by etching spaced recesses into a substrate. The source, drain, and channel regions are defined within this fin. The transistor's gate is wrapped around the channel region of the fin, engaging it on both the top of the fin and the sidewalls of the fin. This configuration allows the gate to induce current flow in the channel from three sides. Thus, FinFET devices have the benefit of higher current flow and reduced short channel effects.
However, fabricating FinFET devices has various challenges. For example, ion implantation, traditionally used for doping planar devices, has been similarly used for doping FinFET devices to create lightly doped source/drain (LDD) regions in the fin. But due to its directional effect, ion implantation has been found ineffective in creating uniform dopant concentration in the three-dimensional fin. For example, the top portion of the fin typically gets much higher dopant concentration than its lower portion, creating so-called shadowing effects. Consequently, not all advantages of the FinFET devices are realized.